This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. X-linked retinoschisis (XLRS) is an inherited form of retinal degeneration affecting young males. It is caused by mutations in a gene (retinoschisin or RS1) that is required for normal retinal function. Patients present with poor vision in infancy or at school age. Visual acuity usually worsens during the teenage years and then stabilizes until complicated by vitreous hemorrhage or retinal detachment during adulthood. In a previous study in a rodent animal model of XLRS, treatment with an AAV-RS1 gene therapy vector resulted in progressive and long-term improvement in retinal function and prevention of retinal cell degeneration. This project is testing the safety and biodistribution of AAV-RS1 vector, injected either subretinally or intravitreally in nonhuman primates, as a critical final step prior to a planned human clinical trial of this potentially sight-saving new therapy. Results indicate that both routes of delivery transduced RS1 to photoreceptors and resulted in expression of the secreted retinoschisin protein.